Method and apparatus for video coding

ABSTRACT

A method of video decoding performed in a video decoder is provided. In the method, coded information of neighboring blocks of a current block is received from a coded video bitstream. The coded information includes intra prediction information of the neighboring blocks. Intra prediction information of the current block is determined based on the coded information of the neighboring blocks. An intra prediction direction mode is determined based on the intra prediction information of the current block. At least one sample of the current block is reconstructed according to the intra prediction direction mode of the current block.

INCORPORATION BY REFERENCE

This present application claims the benefit of priority to U.S.Provisional Application No. 62/819,652, “IMPROVED INTRA MODE CODINGSCHEME” filed on Mar. 17, 2019, which is incorporated by referenceherein in its entirety.

TECHNICAL FIELD

The present disclosure describes embodiments generally related to videocoding.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Video coding and decoding can be performed using inter-pictureprediction with motion compensation. Uncompressed digital video caninclude a series of pictures, each picture having a spatial dimensionof, for example, 1920×1080 luminance samples and associated chrominancesamples. The series of pictures can have a fixed or variable picturerate (informally also known as frame rate), of, for example 60 picturesper second or 60 Hz. Uncompressed video has significant bitraterequirements. For example, 1080p60 4:2:0 video at 8 bit per sample(1920×1080 luminance sample resolution at 60 Hz frame rate) requiresclose to 1.5 Gbit/s bandwidth. An hour of such video requires more than600 gigabytes (GB) of storage space.

One purpose of video coding and decoding can be the reduction ofredundancy in the input video signal, through compression. Compressioncan help reduce the aforementioned bandwidth or storage spacerequirements, in some cases by two orders of magnitude or more. Bothlossless and lossy compression, as well as a combination thereof can beemployed. Lossless compression refers to techniques where an exact copyof the original signal can be reconstructed from the compressed originalsignal. When using lossy compression, the reconstructed signal may notbe identical to the original signal, but the distortion between originaland reconstructed signals is small enough to make the reconstructedsignal useful for the intended application. In the case of video, lossycompression is widely employed. The amount of distortion tolerateddepends on the application; for example, users of certain consumerstreaming applications may tolerate higher distortion than users oftelevision distribution applications. The compression ratio achievablecan reflect that: higher allowable/tolerable distortion can yield highercompression ratios.

A video encoder and decoder can utilize techniques from several broadcategories, including, for example, motion compensation, transform,quantization, and entropy coding.

Video codec technologies can include techniques known as intra coding.In intra coding, sample values are represented without reference tosamples or other data from previously reconstructed reference pictures.In some video codecs, the picture is spatially subdivided into blocks ofsamples. When all blocks of samples are coded in intra mode, thatpicture can be an intra picture. Intra pictures and their derivationssuch as independent decoder refresh pictures, can be used to reset thedecoder state and can, therefore, be used as the first picture in acoded video bitstream and a video session, or as a still image. Thesamples of an intra block can be exposed to a transform, and thetransform coefficients can be quantized before entropy coding. Intraprediction can be a technique that minimizes sample values in thepre-transform domain. In some cases, the smaller the DC value after atransform is, and the smaller the AC coefficients are, the fewer thebits that are required at a given quantization step size to representthe block after entropy coding.

Traditional intra coding such as known from, for example MPEG-2generation coding technologies, does not use intra prediction. However,some newer video compression technologies include techniques thatattempt, from, for example, surrounding sample data and/or metadataobtained during the encoding/decoding of spatially neighboring, andpreceding in decoding order, blocks of data. Such techniques arehenceforth called “intra prediction” techniques. Note that in at leastsome cases, intra prediction is only using reference data from thecurrent picture under reconstruction and not from reference pictures.

There can be many different forms of intra prediction. When more thanone of such techniques can be used in a given video coding technology,the technique in use can be coded in an intra prediction mode. Incertain cases, modes can have submodes and/or parameters, and those canbe coded individually or included in the mode codeword. Which codewordto use for a given mode/submode/parameter combination can have an impactin the coding efficiency gain through intra prediction, and so can theentropy coding technology used to translate the codewords into abitstream.

A certain mode of intra prediction was introduced with H.264, refined inH.265, and further refined in newer coding technologies such as jointexploration model (JEM), versatile video coding (VVC), and benchmark set(BMS). A predictor block can be formed using neighboring sample valuesbelonging to already available samples. Sample values of neighboringsamples are copied into the predictor block according to a direction. Areference to the direction in use can be coded in the bitstream or mayitself be predicted.

Referring to FIG. 1, depicted in the lower right is a subset of ninepredictor directions known from H.265's 33 possible predictor directions(corresponding to the 33 angular modes of the 35 intra modes). The pointwhere the arrows converge (101) represents the sample being predicted.The arrows represent the direction from which the sample is beingpredicted. For example, arrow (102) indicates that sample (101) ispredicted from a sample or samples to the upper right, at a 45 degreeangle from the horizontal. Similarly, arrow (103) indicates that sample(101) is predicted from a sample or samples to the lower left of sample(101), in a 22.5 degree angle from the horizontal.

Still referring to FIG. 1, on the top left there is depicted a squareblock (104) of 4×4 samples (indicated by a dashed, boldface line). Thesquare block (104) includes 16 samples, each labelled with an “S”, itsposition in the Y dimension (e.g., row index) and its position in the Xdimension (e.g., column index). For example, sample S21 is the secondsample in the Y dimension (from the top) and the first (from the left)sample in the X dimension. Similarly, sample S44 is the fourth sample inblock (104) in both the Y and X dimensions. As the block is 4×4 samplesin size, S44 is at the bottom right. Further shown are reference samplesthat follow a similar numbering scheme. A reference sample is labelledwith an R, its Y position (e.g., row index) and X position (columnindex) relative to block (104). In both H.264 and H.265, predictionsamples neighbor the block under reconstruction; therefore no negativevalues need to be used.

Intra picture prediction can work by copying reference sample valuesfrom the neighboring samples as appropriated by the signaled predictiondirection. For example, assume the coded video bitstream includessignaling that, for this block, indicates a prediction directionconsistent with arrow (102)-that is, samples are predicted from aprediction sample or samples to the upper right, at a 45 degree anglefrom the horizontal. In that case, samples S41, S32, S23, and S14 arepredicted from the same reference sample R05. Sample S44 is thenpredicted from reference sample R08.

In certain cases, the values of multiple reference samples may becombined, for example through interpolation, in order to calculate areference sample; especially when the directions are not evenlydivisible by 45 degrees.

The number of possible directions has increased as video codingtechnology has developed. In H.264 (year 2003), nine different directioncould be represented. That increased to 33 in H.265 (year 2013), andJEM/VVC/BMS, at the time of disclosure, can support up to 65 directions.Experiments have been conducted to identify the most likely directions,and certain techniques in the entropy coding are used to represent thoselikely directions in a small number of bits, accepting a certain penaltyfor less likely directions. Further, the directions themselves cansometimes be predicted from neighboring directions used in neighboring,already decoded, blocks.

FIG. 2 shows a schematic (201) that depicts 65 intra predictiondirections according to JEM to illustrate the increasing number ofprediction directions over time.

The mapping of intra prediction directions bits in the coded videobitstream that represent the direction can be different from videocoding technology to video coding technology; and can range, forexample, from simple direct mappings of prediction direction to intraprediction mode, to codewords, to complex adaptive schemes involvingmost probable modes, and similar techniques. In all cases, however,there can be certain directions that are statistically less likely tooccur in video content than certain other directions. As the goal ofvideo compression is the reduction of redundancy, those less likelydirections will, in a well working video coding technology, berepresented by a larger number of bits than more likely directions.

SUMMARY

Aspects of the disclosure provide methods and apparatuses for videoencoding/decoding. In some examples, an apparatus for video decodingincludes receiving circuitry and processing circuitry.

According to an aspect of the disclosure, coded information ofneighboring blocks of a current block is received from a coded videobitstream, where the coded information includes intra predictioninformation of the neighboring blocks. Intra prediction information ofthe current block is determined based on the coded information of theneighboring blocks. An intra prediction direction mode is determinedbased on the intra prediction information of the current block. Further,at least one sample of the current block is reconstructed according tothe intra prediction direction mode of the current block.

In some embodiments, a context model is determined from a set of contextmodels based on the coded information. The intra prediction informationof the current block is determined based on the coded information of theneighboring blocks of the current block according to the determinedcontext model.

In some embodiments, the coded information can include an MPM flag, areference line index, an intra sub-partition (IPS) flag, an intraprediction mode, or an MPM index.

In some embodiments, the intra prediction information of the currentblock can include a most probable mode (MPM) flag, a size of an MPMlist, or an MPM index.

In some embodiments, the context model can be determined based on atleast one of a number of non-angular modes of the neighboring blocks, anumber of angular modes of the neighboring blocks, MPM flags of theneighboring blocks, MPM indices of the neighboring blocks, or ISP flagsof the neighboring blocks.

The size of the MPM list of the current block can be equal to a firstinteger when intra prediction modes of the neighboring blocks arenon-angular modes. The size of the MPM list of the current block can beequal to a second integer when one of the intra prediction modes of theneighboring blocks is an angular mode. The first integer can be smallerthan the second integer.

In addition, the size of the MPM list of the current block can be equalto a first integer when intra prediction modes of the neighboring blocksare non-angular modes. The size of the MPM list of the current block canbe equal to a second integer when one of the intra prediction modes ofthe neighboring blocks is a non-angular mode. The size of the MPM listof the current block can be a third integer when the intra predictionmodes of the neighboring blocks are angular modes. The first integer canbe smaller than the second integer, and the second integer can besmaller than the third integer.

According to an aspect of the disclosure, a method of video decodingperformed in a video decoder is provided. In the method, codedinformation of a current block and neighboring blocks of the currentblock is received from a coded video bitstream, where the codedinformation includes intra prediction information of the current blockand the neighboring blocks. Further, first information associated withthe current block in the coded information is decoded, where the firstinformation indicates whether an intra prediction mode for luma samplesof the current block belongs to selected intra prediction modes. Inaddition, second information associated with the current block in thecoded information is decoded responsive to the first informationindicating that the intra prediction mode for luma samples of thecurrent block belongs to the selected intra prediction modes. The secondinformation indicates whether a most probable mode (MPM) for lumasamples of the current block is an angular mode or a non-angular mode.

In addition, third information associated with the current block in thecoded information is decoded. The third information indicates an MPMindex for the luma samples of the current block, responsive to thesecond information indicating the MPM for the luma samples of thecurrent block is the angular mode. Fourth information associated withthe current block in the coded information is decoded. The fourthinformation indicates whether the MPM of the current block is a Planarmode or a DC mode, responsive to the second information associated withthe current block indicating the MPM for the luma samples of the currentblock is the non-angular mode.

In some embodiments, a context model used for entropy coding the secondinformation associated with the current block is determined based on thefirst information associated with the neighboring blocks or the secondinformation associated with the neighboring blocks.

In some embodiments, the third information associated with the currentblock is coded using a fixed length coding.

Aspects of the disclosure also provide a non-transitorycomputer-readable medium storing instructions which when executed by acomputer for video decoding cause the computer to perform any one or acombination of the methods for video decoding.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a schematic illustration of an exemplary subset of intraprediction modes.

FIG. 2 is an illustration of exemplary intra prediction directions.

FIG. 3 is a schematic illustration of a simplified block diagram of acommunication system (300) in accordance with an embodiment.

FIG. 4 is a schematic illustration of a simplified block diagram of acommunication system (400) in accordance with an embodiment.

FIG. 5 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment.

FIG. 6 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment.

FIG. 7 shows a block diagram of an encoder in accordance with anotherembodiment.

FIG. 8 shows a block diagram of a decoder in accordance with anotherembodiment.

FIG. 9 shows 35 intra prediction modes in accordance with an embodiment.

FIG. 10 shows 87 intra prediction modes in accordance with anembodiment.

FIG. 11 shows positions of neighboring coding block units of a currentcoding block unit in accordance with an embodiment.

FIG. 12 shows four reference lines adjacent to a coding block unit inaccordance with an embodiment.

FIG. 13 shows a first exemplary division of blocks.

FIG. 14 shows a second exemplary division of blocks.

FIG. 15 shows a flow chart outlining a process example according to someembodiments of the disclosure.

FIG. 16 is a schematic illustration of a computer system in accordancewith an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 3 illustrates a simplified block diagram of a communication system(300) according to an embodiment of the present disclosure. Thecommunication system (300) includes a plurality of terminal devices thatcan communicate with each other, via, for example, a network (350). Forexample, the communication system (300) includes a first pair ofterminal devices (310) and (320) interconnected via the network (350).In the FIG. 3 example, the first pair of terminal devices (310) and(320) performs unidirectional transmission of data. For example, theterminal device (310) may code video data (e.g., a stream of videopictures that are captured by the terminal device (310)) fortransmission to the other terminal device (320) via the network (350).The encoded video data can be transmitted in the form of one or morecoded video bitstreams. The terminal device (320) may receive the codedvideo data from the network (350), decode the coded video data torecover the video pictures and display video pictures according to therecovered video data. Unidirectional data transmission may be common inmedia serving applications and the like.

In another example, the communication system (300) includes a secondpair of terminal devices (330) and (340) that performs bidirectionaltransmission of coded video data that may occur, for example, duringvideoconferencing. For bidirectional transmission of data, in anexample, each terminal device of the terminal devices (330) and (340)may code video data (e.g., a stream of video pictures that are capturedby the terminal device) for transmission to the other terminal device ofthe terminal devices (330) and (340) via the network (350). Eachterminal device of the terminal devices (330) and (340) also may receivethe coded video data transmitted by the other terminal device of theterminal devices (330) and (340), and may decode the coded video data torecover the video pictures and may display video pictures at anaccessible display device according to the recovered video data.

In the FIG. 3 example, the terminal devices (310), (320), (330) and(340) may be illustrated as servers, personal computers and smart phonesbut the principles of the present disclosure may be not so limited.Embodiments of the present disclosure find application with laptopcomputers, tablet computers, media players and/or dedicated videoconferencing equipment. The network (350) represents any number ofnetworks that convey coded video data among the terminal devices (310),(320), (330) and (340), including for example wireline (wired) and/orwireless communication networks. The communication network (350) mayexchange data in circuit-switched and/or packet-switched channels.Representative networks include telecommunications networks, local areanetworks, wide area networks and/or the Internet. For the purposes ofthe present discussion, the architecture and topology of the network(350) may be immaterial to the operation of the present disclosureunless explained herein below.

FIG. 4 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and a video decoder ina streaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (413), that caninclude a video source (401), for example a digital camera, creating forexample a stream of video pictures (402) that are uncompressed. In anexample, the stream of video pictures (402) includes samples that aretaken by the digital camera. The stream of video pictures (402),depicted as a bold line to emphasize a high data volume when compared toencoded video data (404) (or coded video bitstreams), can be processedby an electronic device (420) that includes a video encoder (403)coupled to the video source (401). The video encoder (403) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video data (404) (or encoded video bitstream (404)),depicted as a thin line to emphasize the lower data volume when comparedto the stream of video pictures (402), can be stored on a streamingserver (405) for future use. One or more streaming client subsystems,such as client subsystems (406) and (408) in FIG. 4 can access thestreaming server (405) to retrieve copies (407) and (409) of the encodedvideo data (404). A client subsystem (406) can include a video decoder(410), for example, in an electronic device (430). The video decoder(410) decodes the incoming copy (407) of the encoded video data andcreates an outgoing stream of video pictures (411) that can be renderedon a display (412) (e.g., display screen) or other rendering device (notdepicted). In some streaming systems, the encoded video data (404),(407), and (409) (e.g., video bitstreams) can be encoded according tocertain video coding/compression standards. Examples of those standardsinclude ITU-T Recommendation H.265. In an example, a video codingstandard under development is informally known as Versatile Video Coding(VVC). The disclosed subject matter may be used in the context of VVC.

It is noted that the electronic devices (420) and (430) can includeother components (not shown). For example, the electronic device (420)can include a video decoder (not shown) and the electronic device (430)can include a video encoder (not shown) as well.

FIG. 5 shows a block diagram of a video decoder (510) according to anembodiment of the present disclosure. The video decoder (510) can beincluded in an electronic device (530). The electronic device (530) caninclude a receiver (531) (e.g., receiving circuitry). The video decoder(510) can be used in the place of the video decoder (410) in the FIG. 4example.

The receiver (531) may receive one or more coded video sequences to bedecoded by the video decoder (510); in the same or another embodiment,one coded video sequence at a time, where the decoding of each codedvideo sequence is independent from other coded video sequences. Thecoded video sequence may be received from a channel (501), which may bea hardware/software link to a storage device which stores the encodedvideo data. The receiver (531) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (531) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (515) may be coupled inbetween the receiver (531) and an entropy decoder/parser (520) (“parser(520)” henceforth). In certain applications, the buffer memory (515) ispart of the video decoder (510). In others, it can be outside of thevideo decoder (510) (not depicted). In still others, there can be abuffer memory (not depicted) outside of the video decoder (510), forexample to combat network jitter, and in addition another buffer memory(515) inside the video decoder (510), for example to handle playouttiming. When the receiver (531) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosynchronous network, the buffer memory (515) may not be needed, orcan be small. For use on best effort packet networks such as theInternet, the buffer memory (515) may be required, can be comparativelylarge and can be advantageously of adaptive size, and may at leastpartially be implemented in an operating system or similar elements (notdepicted) outside of the video decoder (510).

The video decoder (510) may include the parser (520) to reconstructsymbols (521) from the coded video sequence. Categories of those symbolsinclude information used to manage operation of the video decoder (510),and potentially information to control a rendering device such as arender device (512) (e.g., a display screen) that is not an integralpart of the electronic device (530) but can be coupled to the electronicdevice (530), as was shown in FIG. 5. The control information for therendering device(s) may be in the form of Supplemental EnhancementInformation (SEI messages) or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (520) mayparse/entropy-decode the coded video sequence that is received. Thecoding of the coded video sequence can be in accordance with a videocoding technology or standard, and can follow various principles,including variable length coding, Huffman coding, arithmetic coding withor without context sensitivity, and so forth. The parser (520) mayextract from the coded video sequence, a set of subgroup parameters forat least one of the subgroups of pixels in the video decoder, based uponat least one parameter corresponding to the group. Subgroups can includeGroups of Pictures (GOPs), pictures, tiles, slices, macroblocks, CodingUnits (CUs), blocks, Transform Units (TUs), Prediction Units (PUs) andso forth. The parser (520) may also extract from the coded videosequence information such as transform coefficients, quantizer parametervalues, motion vectors, and so forth.

The parser (520) may perform an entropy decoding/parsing operation onthe video sequence received from the buffer memory (515), so as tocreate symbols (521).

Reconstruction of the symbols (521) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (520). The flow of such subgroup control information between theparser (520) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, the video decoder (510)can be conceptually subdivided into a number of functional units asdescribed below. In a practical implementation operating undercommercial constraints, many of these units interact closely with eachother and can, at least partly, be integrated into each other. However,for the purpose of describing the disclosed subject matter, theconceptual subdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (551). Thescaler/inverse transform unit (551) receives a quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) (521) from the parser (520). The scaler/inversetransform unit (551) can output blocks comprising sample values, thatcan be input into aggregator (555).

In some cases, the output samples of the scaler/inverse transform (551)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (552). In some cases, the intra pictureprediction unit (552) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current picture buffer (558). The currentpicture buffer (558) buffers, for example, partly reconstructed currentpicture and/or fully reconstructed current picture. The aggregator(555), in some cases, adds, on a per sample basis, the predictioninformation the intra prediction unit (552) has generated to the outputsample information as provided by the scaler/inverse transform unit(551).

In other cases, the output samples of the scaler/inverse transform unit(551) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a motion compensation prediction unit (553) canaccess reference picture memory (557) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (521) pertaining to the block, these samples can beadded by the aggregator (555) to the output of the scaler/inversetransform unit (551) (in this case called the residual samples orresidual signal) so as to generate output sample information. Theaddresses within the reference picture memory (557) from where themotion compensation prediction unit (553) fetches prediction samples canbe controlled by motion vectors, available to the motion compensationprediction unit (553) in the form of symbols (521) that can have, forexample X, Y, and reference picture components. Motion compensation alsocan include interpolation of sample values as fetched from the referencepicture memory (557) when sub-sample exact motion vectors are in use,motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (555) can be subject to variousloop filtering techniques in the loop filter unit (556). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video sequence (alsoreferred to as coded video bitstream) and made available to the loopfilter unit (556) as symbols (521) from the parser (520), but can alsobe responsive to meta-information obtained during the decoding ofprevious (in decoding order) parts of the coded picture or coded videosequence, as well as responsive to previously reconstructed andloop-filtered sample values.

The output of the loop filter unit (556) can be a sample stream that canbe output to the render device (512) as well as stored in the referencepicture memory (557) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. For example, once a codedpicture corresponding to a current picture is fully reconstructed andthe coded picture has been identified as a reference picture (by, forexample, the parser (520)), the current picture buffer (558) can becomea part of the reference picture memory (557), and a fresh currentpicture buffer can be reallocated before commencing the reconstructionof the following coded picture.

The video decoder (510) may perform decoding operations according to apredetermined video compression technology in a standard, such as ITU-TRec. H.265. The coded video sequence may conform to a syntax specifiedby the video compression technology or standard being used, in the sensethat the coded video sequence adheres to both the syntax of the videocompression technology or standard and the profiles as documented in thevideo compression technology or standard. Specifically, a profile canselect certain tools as the only tools available for use under thatprofile from all the tools available in the video compression technologyor standard. Also necessary for compliance can be that the complexity ofthe coded video sequence is within bounds as defined by the level of thevideo compression technology or standard. In some cases, levels restrictthe maximum picture size, maximum frame rate, maximum reconstructionsample rate (measured in, for example megasamples per second), maximumreference picture size, and so on. Limits set by levels can, in somecases, be further restricted through Hypothetical Reference Decoder(HRD) specifications and metadata for HRD buffer management signaled inthe coded video sequence.

In an embodiment, the receiver (531) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (510) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or signal noise ratio(SNR) enhancement layers, redundant slices, redundant pictures, forwarderror correction codes, and so on.

FIG. 6 shows a block diagram of a video encoder (603) according to anembodiment of the present disclosure. The video encoder (603) isincluded in an electronic device (620). The electronic device (620)includes a transmitter (640) (e.g., transmitting circuitry). The videoencoder (603) can be used in the place of the video encoder (403) in theFIG. 4 example.

The video encoder (603) may receive video samples from a video source(601) (that is not part of the electronic device (620) in the FIG. 6example) that may capture video image(s) to be coded by the videoencoder (603). In another example, the video source (601) is a part ofthe electronic device (620).

The video source (601) may provide the source video sequence to be codedby the video encoder (603) in the form of a digital video sample streamthat can be of any suitable bit depth (for example: 8 bit, 10 bit, 12bit, . . . ), any color space (for example, BT.601 Y CrCB, RGB, . . . ),and any suitable sampling structure (for example Y CrCb 4:2:0, Y CrCb4:4:4). In a media serving system, the video source (601) may be astorage device storing previously prepared video. In a videoconferencingsystem, the video source (601) may be a camera that captures local imageinformation as a video sequence. Video data may be provided as aplurality of individual pictures that impart motion when viewed insequence. The pictures themselves may be organized as a spatial array ofpixels, wherein each pixel can comprise one or more samples depending onthe sampling structure, color space, etc. in use. A person skilled inthe art can readily understand the relationship between pixels andsamples. The description below focuses on samples.

According to an embodiment, the video encoder (603) may code andcompress the pictures of the source video sequence into a coded videosequence (643) in real time or under any other time constraints asrequired by the application. Enforcing appropriate coding speed is onefunction of a controller (650). In some embodiments, the controller(650) controls other functional units as described below and isfunctionally coupled to the other functional units. The coupling is notdepicted for clarity. Parameters set by the controller (650) can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. The controller (650) can be configured to have other suitablefunctions that pertain to the video encoder (603) optimized for acertain system design.

In some embodiments, the video encoder (603) is configured to operate ina coding loop. As an oversimplified description, in an example, thecoding loop can include a source coder (630) (e.g., responsible forcreating symbols, such as a symbol stream, based on an input picture tobe coded, and a reference picture(s)), and a (local) decoder (633)embedded in the video encoder (603). The decoder (633) reconstructs thesymbols to create the sample data in a similar manner as a (remote)decoder also would create (as any compression between symbols and codedvideo bitstream is lossless in the video compression technologiesconsidered in the disclosed subject matter). The reconstructed samplestream (sample data) is input to the reference picture memory (634). Asthe decoding of a symbol stream leads to bit-exact results independentof decoder location (local or remote), the content in the referencepicture memory (634) is also bit exact between the local encoder andremote encoder. In other words, the prediction part of an encoder “sees”as reference picture samples exactly the same sample values as a decoderwould “see” when using prediction during decoding. This fundamentalprinciple of reference picture synchronicity (and resulting drift, ifsynchronicity cannot be maintained, for example because of channelerrors) is used in some related arts as well.

The operation of the “local” decoder (633) can be the same as of a“remote” decoder, such as the video decoder (510), which has alreadybeen described in detail above in conjunction with FIG. 5. Brieflyreferring also to FIG. 5, however, as symbols are available andencoding/decoding of symbols to a coded video sequence by an entropycoder (645) and the parser (520) can be lossless, the entropy decodingparts of the video decoder (510), including the buffer memory (515), andparser (520) may not be fully implemented in the local decoder (633).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focuses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

During operation, in some examples, the source coder (630) may performmotion compensated predictive coding, which codes an input picturepredictively with reference to one or more previously coded picture fromthe video sequence that were designated as “reference pictures”. In thismanner, the coding engine (632) codes differences between pixel blocksof an input picture and pixel blocks of reference picture(s) that may beselected as prediction reference(s) to the input picture.

The local video decoder (633) may decode coded video data of picturesthat may be designated as reference pictures, based on symbols createdby the source coder (630). Operations of the coding engine (632) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 6), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (633) replicates decodingprocesses that may be performed by the video decoder on referencepictures and may cause reconstructed reference pictures to be stored inthe reference picture cache (634). In this manner, the video encoder(603) may store copies of reconstructed reference pictures locally thathave common content as the reconstructed reference pictures that will beobtained by a far-end video decoder (absent transmission errors).

The predictor (635) may perform prediction searches for the codingengine (632). That is, for a new picture to be coded, the predictor(635) may search the reference picture memory (634) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(635) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (635), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (634).

The controller (650) may manage coding operations of the source coder(630), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (645). The entropy coder (645)translates the symbols as generated by the various functional units intoa coded video sequence, by lossless compressing the symbols according totechnologies such as Huffman coding, variable length coding, arithmeticcoding, and so forth.

The transmitter (640) may buffer the coded video sequence(s) as createdby the entropy coder (645) to prepare for transmission via acommunication channel (660), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(640) may merge coded video data from the video coder (603) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (650) may manage operation of the video encoder (603).During coding, the controller (650) may assign to each coded picture acertain coded picture type, which may affect the coding techniques thatmay be applied to the respective picture. For example, pictures oftenmay be assigned as one of the following picture types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other picture in the sequence as a source ofprediction. Some video codecs allow for different types of intrapictures, including, for example Independent Decoder Refresh (“IDR”)Pictures. A person skilled in the art is aware of those variants of Ipictures and their respective applications and features.

A predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A bi-directionally predictive picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded predictively, viaspatial prediction or via temporal prediction with reference to onepreviously coded reference picture. Blocks of B pictures may be codedpredictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video encoder (603) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video encoder (603) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (640) may transmit additional datawith the encoded video. The source coder (630) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, SEI messages, VUI parameter setfragments, and so on.

A video may be captured as a plurality of source pictures (videopictures) in a temporal sequence. Intra-picture prediction (oftenabbreviated to intra prediction) makes use of spatial correlation in agiven picture, and inter-picture prediction makes uses of the (temporalor other) correlation between the pictures. In an example, a specificpicture under encoding/decoding, which is referred to as a currentpicture, is partitioned into blocks. When a block in the current pictureis similar to a reference block in a previously coded and still bufferedreference picture in the video, the block in the current picture can becoded by a vector that is referred to as a motion vector. The motionvector points to the reference block in the reference picture, and canhave a third dimension identifying the reference picture, in casemultiple reference pictures are in use.

In some embodiments, a bi-prediction technique can be used in theinter-picture prediction. According to the bi-prediction technique, tworeference pictures, such as a first reference picture and a secondreference picture that are both prior in decoding order to the currentpicture in the video (but may be in the past and future, respectively,in display order) are used. A block in the current picture can be codedby a first motion vector that points to a first reference block in thefirst reference picture, and a second motion vector that points to asecond reference block in the second reference picture. The block can bepredicted by a combination of the first reference block and the secondreference block.

Further, a merge mode technique can be used in the inter-pictureprediction to improve coding efficiency.

According to some embodiments of the disclosure, predictions, such asinter-picture predictions and intra-picture predictions are performed inthe unit of blocks. For example, according to the HEVC standard, apicture in a sequence of video pictures is partitioned into coding treeunits (CTU) for compression, the CTUs in a picture have the same size,such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTUincludes three coding tree blocks (CTBs), which are one luma CTB and twochroma CTBs. Each CTU can be recursively quadtree split into one ormultiple coding units (CUs). For example, a CTU of 64×64 pixels can besplit into one CU of 64×64 pixels, or 4 CUs of 32×32 pixels, or 16 CUsof 16×16 pixels. In an example, each CU is analyzed to determine aprediction type for the CU, such as an inter prediction type or an intraprediction type. The CU is split into one or more prediction units (PUs)depending on the temporal and/or spatial predictability. Generally, eachPU includes a luma prediction block (PB), and two chroma PBs. In anembodiment, a prediction operation in coding (encoding/decoding) isperformed in the unit of a prediction block. Using a luma predictionblock as an example of a prediction block, the prediction block includesa matrix of values (e.g., luma values) for pixels, such as 8×8 pixels,16×16 pixels, 8×16 pixels, 16×8 pixels, and the like.

FIG. 7 shows a diagram of a video encoder (703) according to anotherembodiment of the disclosure. The video encoder (703) is configured toreceive a processing block (e.g., a prediction block) of sample valueswithin a current video picture in a sequence of video pictures, andencode the processing block into a coded picture that is part of a codedvideo sequence. In an example, the video encoder (703) is used in theplace of the video encoder (403) in the FIG. 4 example.

In an HEVC example, the video encoder (703) receives a matrix of samplevalues for a processing block, such as a prediction block of 8×8samples, and the like. The video encoder (703) determines whether theprocessing block is best coded using intra mode, inter mode, orbi-prediction mode using, for example, rate-distortion optimization.When the processing block is to be coded in intra mode, the videoencoder (703) may use an intra prediction technique to encode theprocessing block into the coded picture; and when the processing blockis to be coded in inter mode or bi-prediction mode, the video encoder(703) may use an inter prediction or bi-prediction technique,respectively, to encode the processing block into the coded picture. Incertain video coding technologies, merge mode can be an inter pictureprediction submode where the motion vector is derived from one or moremotion vector predictors without the benefit of a coded motion vectorcomponent outside the predictors. In certain other video codingtechnologies, a motion vector component applicable to the subject blockmay be present. In an example, the video encoder (703) includes othercomponents, such as a mode decision module (not shown) to determine themode of the processing blocks.

In the FIG. 7 example, the video encoder (703) includes the interencoder (730), an intra encoder (722), a residue calculator (723), aswitch (726), a residue encoder (724), a general controller (721), andan entropy encoder (725) coupled together as shown in FIG. 7.

The inter encoder (730) is configured to receive the samples of thecurrent block (e.g., a processing block), compare the block to one ormore reference blocks in reference pictures (e.g., blocks in previouspictures and later pictures), generate inter prediction information(e.g., description of redundant information according to inter encodingtechnique, motion vectors, merge mode information), and calculate interprediction results (e.g., predicted block) based on the inter predictioninformation using any suitable technique. In some examples, thereference pictures are decoded reference pictures that are decoded basedon the encoded video information.

The intra encoder (722) is configured to receive the samples of thecurrent block (e.g., a processing block), in some cases compare theblock to blocks already coded in the same picture, generate quantizedcoefficients after transform, and in some cases also intra predictioninformation (e.g., an intra prediction direction information accordingto one or more intra encoding techniques). In an example, the intraencoder (722) also calculates intra prediction results (e.g., predictedblock) based on the intra prediction information and reference blocks inthe same picture.

The general controller (721) is configured to determine general controldata and control other components of the video encoder (703) based onthe general control data. In an example, the general controller (721)determines the mode of the block, and provides a control signal to theswitch (726) based on the mode. For example, when the mode is the intramode, the general controller (721) controls the switch (726) to selectthe intra mode result for use by the residue calculator (723), andcontrols the entropy encoder (725) to select the intra predictioninformation and include the intra prediction information in thebitstream; and when the mode is the inter mode, the general controller(721) controls the switch (726) to select the inter prediction resultfor use by the residue calculator (723), and controls the entropyencoder (725) to select the inter prediction information and include theinter prediction information in the bitstream.

The residue calculator (723) is configured to calculate a difference(residue data) between the received block and prediction resultsselected from the intra encoder (722) or the inter encoder (730). Theresidue encoder (724) is configured to operate based on the residue datato encode the residue data to generate the transform coefficients. In anexample, the residue encoder (724) is configured to convert the residuedata from a spatial domain to a frequency domain, and generate thetransform coefficients. The transform coefficients are then subject toquantization processing to obtain quantized transform coefficients. Invarious embodiments, the video encoder (703) also includes a residuedecoder (728). The residue decoder (728) is configured to performinverse-transform, and generate the decoded residue data. The decodedresidue data can be suitably used by the intra encoder (722) and theinter encoder (730). For example, the inter encoder (730) can generatedecoded blocks based on the decoded residue data and inter predictioninformation, and the intra encoder (722) can generate decoded blocksbased on the decoded residue data and the intra prediction information.The decoded blocks are suitably processed to generate decoded picturesand the decoded pictures can be buffered in a memory circuit (not shown)and used as reference pictures in some examples.

The entropy encoder (725) is configured to format the bitstream toinclude the encoded block. The entropy encoder (725) is configured toinclude various information according to a suitable standard, such asthe HEVC standard. In an example, the entropy encoder (725) isconfigured to include the general control data, the selected predictioninformation (e.g., intra prediction information or inter predictioninformation), the residue information, and other suitable information inthe bitstream. Note that, according to the disclosed subject matter,when coding a block in the merge submode of either inter mode orbi-prediction mode, there is no residue information.

FIG. 8 shows a diagram of a video decoder (810) according to anotherembodiment of the disclosure. The video decoder (810) is configured toreceive coded pictures that are part of a coded video sequence, anddecode the coded pictures to generate reconstructed pictures. In anexample, the video decoder (810) is used in the place of the videodecoder (410) in the FIG. 4 example.

In the FIG. 8 example, the video decoder (810) includes an entropydecoder (871), an inter decoder (880), a residue decoder (873), areconstruction module (874), and an intra decoder (872) coupled togetheras shown in FIG. 8.

The entropy decoder (871) can be configured to reconstruct, from thecoded picture, certain symbols that represent the syntax elements ofwhich the coded picture is made up. Such symbols can include, forexample, the mode in which a block is coded (such as, for example, intramode, inter mode, bi-predicted mode, the latter two in merge submode oranother submode), prediction information (such as, for example, intraprediction information or inter prediction information) that canidentify certain sample or metadata that is used for prediction by theintra decoder (872) or the inter decoder (880), respectively, residualinformation in the form of, for example, quantized transformcoefficients, and the like. In an example, when the prediction mode isinter or bi-predicted mode, the inter prediction information is providedto the inter decoder (880); and when the prediction type is the intraprediction type, the intra prediction information is provided to theintra decoder (872). The residual information can be subject to inversequantization and is provided to the residue decoder (873).

The inter decoder (880) is configured to receive the inter predictioninformation, and generate inter prediction results based on the interprediction information.

The intra decoder (872) is configured to receive the intra predictioninformation, and generate prediction results based on the intraprediction information.

The residue decoder (873) is configured to perform inverse quantizationto extract de-quantized transform coefficients, and process thede-quantized transform coefficients to convert the residual from thefrequency domain to the spatial domain. The residue decoder (873) mayalso require certain control information (to include the QuantizerParameter (QP)), and that information may be provided by the entropydecoder (871) (data path not depicted as this may be low volume controlinformation only).

The reconstruction module (874) is configured to combine, in the spatialdomain, the residual as output by the residue decoder (873) and theprediction results (as output by the inter or intra prediction modulesas the case may be) to form a reconstructed block, that may be part ofthe reconstructed picture, which in turn may be part of thereconstructed video. It is noted that other suitable operations, such asa deblocking operation and the like, can be performed to improve thevisual quality.

It is noted that the video encoders (403), (603), and (703), and thevideo decoders (410), (510), and (810) can be implemented using anysuitable technique. In an embodiment, the video encoders (403), (603),and (703), and the video decoders (410), (510), and (810) can beimplemented using one or more integrated circuits. In anotherembodiment, the video encoders (403), (603), and (603), and the videodecoders (410), (510), and (810) can be implemented using one or moreprocessors that execute software instructions.

The present disclosure is directed to a set of advanced video codingtechnologies, including an improved intra mode coding scheme.

A total of 35 intra prediction modes is illustrated in FIG. 9, forexample as used in HEVC. Among the 35 intra prediction modes, mode 10 isa horizontal mode and mode 26 is a vertical mode. Modes 2, 18, and 34are diagonal modes. The 35 intra prediction modes can be signalled bythree most probable modes (MPMs) and 32 remaining modes.

A total of 95 intra prediction modes is illustrated in in FIG. 10, forexample as used in VVC. Mode 18 is a horizontal mode and mode 50 is avertical mode. Modes 2, 34, and 66 are diagonal modes. Modes −1 to −14and Modes 67 to 80 can be referred to as Wide-Angle Intra Prediction(WAIP) modes.

An MPM list of size 3 can be generated based on intra prediction modesof neighboring blocks of the current block, for example in HEVC. The MPMlist can also be referred to as a primary MPM list. If an intraprediction mode of the current block is not from the MPM list, a flag,for example a MPM flag, can be signalled to indicate whether the intraprediction mode of the current block belongs to selected modes, forexample other candidate intra prediction modes different from the intraprediction modes in the MPM list.

An example of the MPM list generation process is shown in the followingsyntax elements:

If (leftIntraDir==aboveIntraDir && leftIntraDir>DC_IDX)

-   -   MPM [0]=leftIntraDir;    -   MPM [1]=((leftIntraDir+offset) % mod)+2;    -   MPM [2]=((leftIntraDir−1) % mod)+2;

Else if (leftIntraDir==aboveIntraDir)

-   -   MPM [0]=PLANAR_IDX;    -   MPM [1]=DC_IDX;    -   MPM [2]=VER_IDX;

Else if (leftIntraDir !=aboveIntraDir)

-   -   MPM [0]=leftIntraDir;    -   MPM [1]=aboveIntraDir;    -   If (leftIntraDir>0 && aboveIntraDir>0)        -   MPM [2]=PLANAR_IDX;    -   Else        -   MPM [2]=(leftIntraDir+aboveIntraDir)<2 ? VER_IDX: DC_IDX;            In the example syntax elements above, leftIntraDir is used            to indicate the mode in an adjacent block to the left of the            current block (“left block”); and aboveIntraDir is used to            indicate the mode in an adjacent block above the current            block (“above block”). If the left block or the above block            is currently not available, leftIntraDir or aboveIntraDir            can be set to an index for intra DC mode (e.g., DC_IDX). In            addition, variables “offset” and “mod” are constant values,            which can be set to be 29 and 32, respectively, in one            example.

A size of an MPM list can be set to be equal to 6 for both an adjacentreference line (also referred to as zero reference line) andnon-adjacent reference lines (also referred to non-zero referencelines), for example in VVC Test Model 3 (VTM3). The positions ofneighboring modes used to derive the 6 MPM candidates can also be thesame for the adjacent and non-adjacent reference lines, as illustratedin FIG. 11 for example. As shown in FIG. 11, the block A and block Bdenote exemplary above and left neighboring coding units of a currentcoding unit 1100. Variables candIntraPredModeA and candIntraPredModeBindicate the associated intra prediction modes of the blocks A and B,respectively. In addition, candIntraPredModeA and candIntraPredModeB canbe initially set to be equal to INTRA_PLANAR. If the block A (or B) ismarked as available, candIntraPredModeA (or candIntraPredModeB) is setto be equal to the actual intra prediction mode of the block A (or B).

An MPM candidate derivation process (or MPM list derivation process) ofthe current coding unit 1100 can be different between an adjacentreference line (or zero reference line) and non-adjacent reference lines(or non-zero reference lines) of the current coding unit 1100. For thezero reference line, when both neighboring modes are Planar or DC mode,default modes can be used to construct the MPM list. Two of the defaultmodes can be Planar and DC modes, and the remaining 4 modes can beangular modes (also referred to as angular default modes). For thenon-zero reference lines, when both neighboring modes are Planar or DCmode, 6 angular default modes can be used to construct the MPM list. Anexemplary MPM list derivation process is shown in the syntax elementsbelow. In the syntax elements below, candModeList[x] with x=0 . . . 5denotes the 6 MPM candidates, IntraLumaRefLineIdx[xCb][yCb] denotes thereference line index of the block (or current coding unit) to bepredicted, and IntraLumaRefLineIdx[xCb][yCb] can be 0, 1, or 3.

-   -   If candIntraPredModeB is equal to candIntraPredModeA and        candIntraPredModeA is greater than INTRA_DC, candModeList[x]        with x=0 . . . 5 is derived as follows:        -   If IntraLumaRefLineIdx[xCb][yCb] is equal to 0, the            following applies:            -   candModeList[0]=candIntraPredModeA            -   candModeList[1]=INTRA_PLANAR            -   candModeList[2]=INTRA_DC            -   candModeList[3]=2+((candIntraPredModeA+61) % 64)            -   candModeList[4]=2+((candIntraPredModeA−1) % 64)            -   candModeList[5]=2+((candIntraPredModeA+60) % 64)        -   Otherwise (IntraLumaRefLineIdx[xCb][yCb] is not equal to 0),            the following applies:            -   candModeList[0]=candIntraPredModeA            -   candModeList[1]=2+((candIntraPredModeA+61) % 64)            -   candModeList[2]=2+((candIntraPredModeA−1) % 64)            -   candModeList[3]=2+((candIntraPredModeA+60) % 64)            -   candModeList[4]=2+(candIntraPredModeA % 64)            -   candModeList[5]=2+((candIntraPredModeA+59) % 64)    -   Otherwise if candIntraPredModeB is not equal to        candIntraPredModeA and candIntraPredModeA or candIntraPredModeB        is greater than INTRA_DC, the following applies:        -   The variables minAB and maxAB are derived as follows:        -   minAB=candModeList[(candModeList[0]>candModeList[1])? 1: 0]        -   maxAB=candModeList[(candModeList[0]>candModeList[1])? 0: 1]        -   If candIntraPredModeA and candIntraPredModeB are both            greater than INTRA_DC, candModeList[x] with x=0 . . . 5 is            derived as follows:            -   candModeList[0]=candIntraPredModeA            -   candModeList[1]=candIntraPredModeB        -   If IntraLumaRefLineIdx[xCb][yCb] is equal to 0, the            following applies:            -   candModeList[2]=INTRA_PLANAR            -   candModeList[3]=INTRA_DC        -    If maxAB−minAB is in the range of 2 to 62, inclusive, the            following applies:            -   candModeList[4]=2+((maxAB+61) % 64)            -   candModeList[5]=2+((maxAB−1) % 64)        -    Otherwise, the following applies:            -   candModeList[4]=2+((maxAB+60) % 64)            -   candModeList[5]=2+((maxAB) % 64)        -    Otherwise (IntraLumaRefLineIdx[xCb][yCb] is not equal to            0), the following applies:        -   If maxAB−minAB is equal to 1, the following applies:            -   candModeList[2]=2+((minAB+61) % 64)            -   candModeList[3]=2+((maxAB−1) % 64)            -   candModeList[4]=2+((minAB+60) % 64)            -   candModeList[5]=2+(maxAB % 64)        -   Otherwise if maxAB−minAB is equal to 2, the following            applies:            -   candModeList[2]=2+((minAB−1) % 64)            -   candModeList[3]=2+((minAB+61) % 64)            -   candModeList[4]=2+((maxAB−1) % 64)            -   candModeList[5]=2+((minAB+60) % 64)        -   Otherwise if maxAB−minAB is greater than 61, the following            applies:            -   candModeList[2]=2+((minAB−1) % 64)            -   candModeList[3]=2+((maxAB+61) % 64)            -   candModeList[4]=2+(minAB % 64)            -   candModeList[5]=2+((maxAB+60) % 64)        -   Otherwise, the following applies:            -   candModeList[2]=2+((minAB+61) % 64)            -   candModeList[3]=2+((minAB−1) % 64)            -   candModeList[4]=2+((maxAB+61) % 64)            -   candModeList[5]=2+((maxAB−1) % 64)    -   Otherwise (candIntraPredModeA or candIntraPredModeB is greater        than INTRA_DC), candModeList[x] with x=0 . . . 5 is derived as        follows:        -   If IntraLumaRefLineIdx[xCb][yCb] is equal to 0, the            following applies:            -   candModeList[0]=candIntraPredModeA            -   candModeList[1]=candIntraPredModeB            -   candModeList[2]=1−minAB            -   candModeList[3]=2+((maxAB+61) % 64)            -   candModeList[4]=2+((maxAB−1) % 64)            -   candModeList[5]=2+((maxAB+60) % 64)        -   Otherwise (IntraLumaRefLineIdx[xCb][yCb] is not equal to 0),            the following applies:            -   candModeList[0]=maxAB            -   candModeList[1]=2+((maxAB+61) % 64)            -   candModeList[2]=2+((maxAB−1) % 64)            -   candModeList[3]=2+((maxAB+60) % 64)            -   candModeList[4]=2+(maxAB % 64)            -   candModeList[5]=2+((maxAB+59) % 64)

Otherwise, the following applies:

-   -   If IntraLumaRefLineIdx[xCb][yCb] is equal to 0, the following        applies:        -   candModeList[0]=candIntraPredModeA        -   candModeList[1]=candModeList[0]==            -   INTRA_PLANAR)? INTRA_DC: INTRA_PLANAR        -   candModeList[2]=INTRA_ANGULAR50        -   candModeList[3]=INTRA_ANGULAR18        -   candModeList[4]=INTRA_ANGULAR46        -   candModeList[5]=INTRA_ANGULAR54    -   Otherwise (IntraLumaRefLineIdx[xCb][yCb] is not equal to 0), the        following applies:        -   candModeList[0]=INTRA_ANGULAR50        -   candModeList[1]=INTRA_ANGULAR18        -   candModeList[2]=INTRA_ANGULAR2        -   candModeList[3]=INTRA_ANGULAR34        -   candModeList[4]=INTRA_ANGULAR66        -   candModeList[5]=INTRA_ANGULAR26

In multi-line intra prediction, additional reference lines can be usedfor intra prediction. An encoder can determine and signal whichreference line is used to generate the intra predictor. The referenceline index can be signaled before intra prediction modes, and only themost probable modes can be allowed in case a nonzero reference lineindex is signaled. In FIG. 12, an example of 4 reference lines (e.g.,reference lines 0-3) is depicted, where each of the four reference linesis composed of six segments, i.e., Segments A to F, together with thetop-left reference sample. In addition, the Segments A and F can bepadded with the closest samples from the Segments B and E, respectively.

In an Intra Sub-Partitions (ISP) coding mode, luma intra-predictedblocks can be divided vertically or horizontally into sub-partitions(e.g., 2 or 4) depending on block size dimensions, as shown in Table 1for example. FIGS. 13 and 14 show examples of two possibilities ofdivision of a luma intra-predicted block based on the ISP coding mode.FIG. 13 illustrates an exemplary division of a 4×8 block or an 8×4block. FIG. 15 illustrates an exemplary division of a block that is notone of a 4×8 block, an 8×4 block, or a 4×4 block. All sub-partitionsfulfill the condition of having at least 16 samples in one example.

TABLE 1 Number of sub-partitions depending on the block size Block SizeNumber of Sub-Partitions 4 × 4 Not divided 4 × 8 and 8 × 4 2 All othercases 4

For each of the sub-partitions, a residual signal can be generated byentropy decoding the coefficients sent by an encoder and then inversequantizing and inverse transforming the coefficients. Further, thesub-partition is intra predicted and the corresponding reconstructedsamples can be obtained by adding the residual signal to a predictionsignal. Therefore, the reconstructed values of each sub-partition can beavailable to generate the prediction of the next one, which can repeatthe process and so on. All sub-partitions can share the same intraprediction mode.

Based on the intra prediction mode and the split that is utilized, twodifferent classes of processing orders can be used, which can bereferred to as a normal order and a reversed order. In the normal order,the first sub-partition to be processed contains the top-left sample ofthe CU. The processing then continues downwards (e.g., for a horizontalsplit) or rightwards (e.g., for a vertical split). As a result,reference samples used to generate the prediction signals of thesub-partitions are only located at the left and above sides of thelines. On the other hand, the reverse processing order (or reverseorder) either (i) starts with a sub-partition that contains thebottom-left sample of the CU and continues upwards or (ii) starts with asub-partition that contains the top-right sample of the CU and continuesleftwards.

In some embodiments, the ISP algorithm is only tested with intraprediction modes that are part of the MPM list. For this reason, if ablock uses the ISP mode, then the MPM flag can be inferred to be one. Ifthe ISP mode is used for a certain block, then the MPM list can bemodified to exclude the DC mode and to prioritize horizontal intraprediction modes for the ISP horizontal split and vertical intraprediction modes for the ISP vertical split.

When Planar and DC modes are always included in the MPM list, forexample in VTM4, and both neighboring modes are Planar/DC modes, acurrent mode may have a high probability to be Planar or DC mode.Embodiments of the present disclosure include utilizing this correlationin the design of current intra prediction mode coding. As furtherdescribed below, in some embodiments, a context used for entropy codingintra prediction information of a current block is dependent on codedinformation of neighboring blocks. Further, in some embodiments, syntaxelements for signaling whether a selected MPM is an angular mode and/orPlanar or DC mode is selected are provided.

As described above, the line index of an adjacent, or nearest, referenceline is 0 (zero reference line), and other lines are called non-zeroreference lines. Further, candModeList denotes the MPM list, RefLineldxdenotes the reference line index of a current block, andcandlntraPredModeA and candlntraPredModeB denote the left and aboveneighboring intra prediction modes. Each intra prediction mode isassociated with a mode number (also called intra prediction mode index).For example, in VVC, Planar, DC, and horizontal and vertical intraprediction modes can be associated with mode numbers 0, 1, 18 and 50,respectively. The MPM index of the first candidate in the MPM list canbe denoted as 0, and the MPM index of second candidate can be denote as1, and so on.

If a neighboring intra prediction mode is not Planar or DC mode, or ifthe neighboring intra prediction mode generates prediction samplesaccording to a given prediction direction, such as an intra predictionmode from mode 2 to mode 66, for example as defined in VVC draft 2, theneighboring intra prediction mode is an angular mode. If the neighboringintra prediction mode does not indicate a directional intra prediction,such as Planar or DC mode, the neighboring intra prediction mode is anon-angular mode.

In some embodiments, a context (or context model) used for entropycoding of a MPM flag of a current block can be dependent on codedinformation of the current block and/or neighboring blocks of thecurrent block. The coded information can include but is not limited to aMPM flag, a reference line index, an ISP type (e.g., verticalsub-partition, horizontal sub-partition, or no sub-partition), an intraprediction mode, a MPM index, etc.

In an embodiment, coding information of the current block (e.g.,reference line index and/or ISP type), which can be decoded before othercoding information such as an MPM flag and/or an intra prediction modeof the current block, can be used for entropy coding of the MPM flag andintra prediction mode of the current block.

In one embodiment, the context used for entropy coding of the MPM flagof the current block can be dependent on a number of non-angular (orangular) modes of the neighboring blocks. In a first example, if bothintra prediction modes of the neighboring blocks are non-angular modes,a first context is used. If only one of the intra prediction modes ofthe neighboring blocks is a non-angular mode, a second context is used.If both intra prediction modes of the neighboring blocks are angularmodes, a third context is used. In a second example, if at least one ofthe intra prediction modes of the neighboring blocks is a non-angularmode, a first context is used. If both of the intra prediction modes ofthe neighboring blocks are angular modes, a second context is used. In athird example, the context used for entropy coding of the MPM flag isdependent on how many modes of neighboring blocks are Planar modes. In afourth example, the context used for entropy coding of the MPM flag isdependent on how many modes of neighboring blocks are Planar or DCmodes.

The number of contexts for entropy coding of the MPM flag can bedependent on how many neighboring modes are used. For example, if thenumber of neighboring blocks used is N, the number of the context usedfor entropy coding of the MPM flag can be equal to K*(N+1), where K canbe any positive integer such as 1 or 2.

In one embodiment, the context used for entropy coding of the MPM flagof the current block can be dependent on MPM flags of the neighboringblocks. In a first example, if both MPM flags of the neighboring blocksare true, a first context is used. If only one of the MPM flags of theneighboring blocks is true, a second context is used. If none of the MPMflags of the neighboring blocks is true, a third context is used. In asecond example, if at least one of the MPM flags of the neighboringblocks is true, the first context is used. I If none of the MPM flags ofthe neighboring blocks is true, the second context is used. In a thirdexample, the number of contexts for entropy coding of the MPM flag canbe dependent on how many MPM flags of the neighboring modes (or blocks)are true. For example, if the number of neighboring blocks used is N,the number of the context used for entropy coding of the MPM flag can beequal to K*(N+1), where K can be any positive integer such as 1 or 2.

In one embodiment, the context used for entropy coding of the MPM flagof the current block is dependent on the MPM flags of neighboring modeand/or the number of non-angular (or angular) MPMs of the neighboringblocks. For example, if both neighboring modes are non-angular MPMs, afirst context is used. If both neighboring modes are MPMs that caninclude angular MPMs and non-angular MPMs, a second context is used. Ifonly one of the neighboring modes is MPM, a third context is used.Otherwise, none of the neighboring modes is a MPM, a fourth context isused.

In one embodiment, the context used for entropy coding of the MPM flagis dependent on the MPM flags and/or MPM indices of the neighboringblocks. In one embodiment, the context used for entropy coding of theMPM flag is dependent on the MPM flags and/or ISP flags of theneighboring blocks. Further, in further examples, the context used forentropy coding of the MPM flag can be dependent on other codedinformation or combinations of coded information.

In some embodiments, a size of a MPM list of the current block can bedependent on coded information of a current block, for example asdescribed above, and/or neighboring blocks of the current block. Thecoded information can include but is not limited to intra predictionmodes, a MPM flag, an ISP flag, a MPM index, a reference line index,etc. In one embodiment, the size of the MPM list is dependent on thenumber of non-angular (or angular) modes of neighboring blocks. In afirst example, when both the neighboring modes are non-angular modes,the size of the MPM list is equal to K1. When one of the neighboringmodes is an angular mode, the size of the MPM list is equal to K2. K1and K2 are positive integers, and K1 is smaller than K2. For example, K1can be set equal to 2. In a second example, when both the neighboringmodes are non-angular modes, the size of the MPM list can be equal toK1. When only one of the neighboring modes is a non-angular mode, thesize of the MPM list can be equal to K2. When none of the neighboringmodes is non-angular mode, the size of the MPM list is equal to K3. K1,K2, and K3 are positive integers. In addition, K1 can be smaller thanK2, and K2 can be smaller than K3. For example, K1 can be set equal to2, and K2 can be set equal to 5.

In some embodiments, instead of signaling a MPM index when a MPM flag ofthe current block is true, a new syntax element, for example,intra_luma_ang_mpm_flag, can be signaled to indicate whether a selectedMPM is an angular mode or not. If intra_luma_ang_mpm_flag is true,another flag intra_luma_planar_flag can be signaled to indicate whetherPlanar or DC mode is selected. Exemplary syntax changes and semanticsare shown in Table 2.

TABLE 2 Syntax changes and semantics to the new syntax elementintra_luma_ang_mpm_flag if( intra_luma_ref_idx[ x0 ][ y0 ] = = 0 &&intra_subpartitions_mode_flag[ x0 ][ y0 ] = = 0 ) intra_luma_mpm_flag[x0 ][ y0 ] ae(v) if( intra_luma_mpm_flag[ x0 ][ y0 ] )intra_luma_ang_mpm_flag[ x0 ][ y0 ] ae(v) if( intra_luma_ang_mpm_flag[x0 ][ y0 ] ) intra_luma_mpm_idx[ x0 ][ y0 ] ae(v) elseintra_luma_planar_flag[ x0 ][ y0 ] ae(v) else intra_luma_mpm_remainder[x0 ][ y0 ] ae(v)

As shown in Table 2, when the syntax elementintra_luma_ref_idx[x0][y0]==0 (e.g., the reference line for the currentblock is reference line 0) and the syntax elementintra_subpartitions_mode_flag[x0][y0]==0 (e.g., the ISP mode is notapplied), intra_luma_mpm_flag[x0][y0] is signaled. Theintra_luma_mpm_flag[x0][y0] indicates whether the intra prediction modefor luma samples of the current block belongs to selected intraprediction modes (e.g., other candidate intra prediction modes that aredifferent from the intra prediction modes in the MPM list). When theintra_luma_mpm_flag[x0][y0] is true (e.g., the intra prediction mode forluma samples of the current block belongs to the selected intraprediction modes), the intra_luma_ang_mpm_flag[x0][y0] can be signaled.The intra_luma_ang_mpm_flag[x0][y0] can specify whether the intraprediciton mode for luma samples of the current block is an angular modeor an non-angular mode, where the angular mode is an intra predicitonmode that is not Planar or DC mode. The array indices x0, y0 specify thelocation (x0, y0) of the top-left luma sample of the considered codingblock (or current block) relative to the top-left luma sample of thepicture. When the intra_luma_ang_mpm_flag[x0][y0] is true (e.g., theintra prediciton mode for luma samples of the current block is anangular mode), the intra_luma_mpm_idx[x0][y0] can be signaled. Theintra_luma_mpm_idx[x0][y0] indicates an MPM index for the luma samplesof the current block.

When the intra_luma_ang_mpm_flag[x0][y0] is not true (e.g., the intraprediction mode for luma samples of the current block is a non-angularmode), the intra_luma_planar_flag[x0][y0] can be signaled. Theintra_luma_planar_flag[x0][y0] can specify whether the intra predicitonmode for luma samples of the current block is Planar or DC. The arrayindices x0, y0 specify the location (x0, y0) of the top-left luma sampleof the considered coding block (or current block) relative to thetop-left luma sample of the picture.

When the intra_luma_mpm_flag[x0][y0] is not true (e.g., the intraprediction mode for luma samples of the current block does not belong tothe selected intra prediction modes), theintra_luma_mpm_remainder[x0][y0] can be signaled. Theintra_luma_mpm_remainder[x0][y0] can indicate the intra prediction modefor luma samples of the current block belongs to the remainingcandidates other than the selected intra prediction modes.

In one embodiment, the intra_luma_mpm_idx[x0][y0] can be coded usingfixed length coding (e.g., coded using 2-bit). In one embodiment, theintra_luma_ang_mpm_flag[x0][y0] can be entropy coded, and the contextused for entropy coding of the intra_luma_ang_mpm_flag[x0][y0] can bederived from values of the intra_luma_mpm_flag of neighboring blocks. Inone embodiment, the intra_luma_ang_mpm_flag[x0][y0] can be entropycoded, and the context used for entropy coding of theintra_luma_ang_mpm_flag[x0][y0] can be derived from values of theintra_luma_ang_mpm_flag of neighboring blocks.

In some embodiments, the context of the entropy coding of a MPM index ofthe current block can be dependent on the coded information of theneighboring blocks of the current block, where the coded information caninclude but is not limited to the intra prediction modes, a MPM flag, aMPM index, a reference line index, an ISP flag of neighboring blocks,etc. In one embodiment, the context of the entropy coding of the MPMindex can be dependent on the number of angular modes of the neighboringblocks. For example, the context of the entropy coding of a first bin ofthe MPM index is dependent on the number of angular modes of theneighboring blocks. In one embodiment, the context of the entropy codingof the MPM index can be dependent on the number of neighboring modesthat are intra prediction modes larger than a Planar mode. For example,the context of the entropy coding of the first bin of MPM index isdependent on the number of neighboring modes whose intra prediction modenumber are greater than the Planar mode.

FIG. 15 shows a flow chart outlining a process (1500) according to anembodiment of the disclosure. The process (1500) can be used in thereconstruction of a block coded in intra mode, so to generate aprediction block for the block under reconstruction. In variousembodiments, the process (1500) are executed by processing circuitry,such as the processing circuitry in the terminal devices (310), (320),(330) and (340), the processing circuitry that performs functions of thevideo encoder (403), the processing circuitry that performs functions ofthe video decoder (410), the processing circuitry that performsfunctions of the video decoder (510), the processing circuitry thatperforms functions of the video encoder (603), and the like. In someembodiments, the process (1500) is implemented in software instructions,thus when the processing circuitry executes the software instructions,the processing circuitry performs the process (1500). The process startsat (S1501) and proceeds to (S1510).

At (1510), coded information of neighboring blocks of a current blockcan be received from a coded video bitstream. The coded information caninclude intra prediction information of the neighboring blocks. In someembodiments, the coded information can include an MPM flag, a referenceline index, an intra sub-partition (IPS) flag, an intra prediction mode,or an MPM index.

At (1520), intra prediction information of the current block can bedetermined based on the coded information of the neighboring blocks. Insome embodiments, the intra prediction information of the current blockcan include a most probable mode (MPM) flag, a size of an MPM list, oran MPM index. In some embodiments, in order to determine the intraprediction information of the current block, a context model can bedetermined from a set of context models based on the coded information,and the intra prediction information of the current block can bedetermined based on the coded information of the neighboring blocks ofthe current block according to the determined context model.

In some embodiments, the context model can be determined based on atleast one of a number of non-angular modes of the neighboring blocks, anumber of angular modes of the neighboring blocks, MPM flags of theneighboring blocks, MPM indices of the neighboring blocks, or ISP flagsof the neighboring blocks.

In some embodiments, the size of the MPM list of the current block canbe equal to a first integer when intra prediction modes of theneighboring blocks are non-angular modes, and the size of the MPM listof the current block can be equal to a second integer when one of theintra prediction modes of the neighboring blocks is an angular mode,where the first integer is smaller than the second integer.

In some embodiments, the size of the MPM list of the current block canbe equal to a first integer when intra prediction modes of theneighboring blocks are non-angular modes, the size of the MPM list ofthe current block can be equal to a second integer when one of the intraprediction modes of the neighboring blocks is a non-angular mode, andthe size of the MPM list of the current block can be a third integerwhen the intra prediction modes of the neighboring blocks are angularmodes. The first integer is smaller than the second integer, and thesecond integer is smaller than the third integer.

At (1530), an intra prediction direction mode can be determined based onthe intra prediction information of the current block. At (1540), atleast one sample of the current block can be reconstructed according tothe intra prediction direction mode of the current block.

The methods described in the present disclosure may be used separatelyor combined in any order. Further, in each of the methods (orembodiments), an encoder, and a decoder may be implemented by processingcircuitry (e.g., one or more processors or one or more integratedcircuits). In one example, the one or more processors execute a programthat is stored in a non-transitory computer-readable medium. Further,the term of a block may be interpreted as a prediction block, a codingblock, or a coding unit, i.e., CU.

The techniques described above, can be implemented as computer softwareusing computer-readable instructions and physically stored in one ormore computer-readable media. For example, FIG. 16 shows a computersystem (1600) suitable for implementing certain embodiments of thedisclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by one or more computer central processingunits (CPUs), Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 16 for computer system (1600) are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system (1600).

Computer system (1600) may include certain human interface inputdevices. Such a human interface input device may be responsive to inputby one or more human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard (1601), mouse (1602), trackpad (1603), touchscreen (1610), data-glove (not shown), joystick (1605), microphone(1606), scanner (1607), camera (1608).

Computer system (1600) may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen (1610), data-glove (not shown), or joystick (1605), butthere can also be tactile feedback devices that do not serve as inputdevices), audio output devices (such as: speakers (1609), headphones(not depicted)), visual output devices (such as screens (1610) toinclude CRT screens, LCD screens, plasma screens, OLED screens, eachwith or without touch-screen input capability, each with or withouttactile feedback capability—some of which may be capable to output twodimensional visual output or more than three dimensional output throughmeans such as stereographic output; virtual-reality glasses (notdepicted), holographic displays and smoke tanks (not depicted)), andprinters (not depicted).

Computer system (1600) can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW(1620) with CD/DVD or the like media (1621), thumb-drive (1622),removable hard drive or solid state drive (1623), legacy magnetic mediasuch as tape and floppy disc (not depicted), specialized ROM/ASIC/PLDbased devices such as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system (1600) can also include an interface to one or morecommunication networks. Networks can for example be wireless, wireline,optical. Networks can further be local, wide-area, metropolitan,vehicular and industrial, real-time, delay-tolerant, and so on. Examplesof networks include local area networks such as Ethernet, wireless LANs,cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TVwireline or wireless wide area digital networks to include cable TV,satellite TV, and terrestrial broadcast TV, vehicular and industrial toinclude CANBus, and so forth. Certain networks commonly require externalnetwork interface adapters that attached to certain general purpose dataports or peripheral buses (1649) (such as, for example USB ports of thecomputer system (1600)); others are commonly integrated into the core ofthe computer system (1600) by attachment to a system bus as describedbelow (for example Ethernet interface into a PC computer system orcellular network interface into a smartphone computer system). Using anyof these networks, computer system (1600) can communicate with otherentities. Such communication can be uni-directional, receive only (forexample, broadcast TV), uni-directional send-only (for example CANbus tocertain CANbus devices), or bi-directional, for example to othercomputer systems using local or wide area digital networks. Certainprotocols and protocol stacks can be used on each of those networks andnetwork interfaces as described above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core (1640) of thecomputer system (1600).

The core (1640) can include one or more Central Processing Units (CPU)(1641), Graphics Processing Units (GPU) (1642), specialized programmableprocessing units in the form of Field Programmable Gate Areas (FPGA)(1643), hardware accelerators for certain tasks (1644), and so forth.These devices, along with Read-only memory (ROM) (1645), Random-accessmemory (1646), internal mass storage such as internal non-useraccessible hard drives, SSDs, and the like (1647), may be connectedthrough a system bus (1648). In some computer systems, the system bus(1648) can be accessible in the form of one or more physical plugs toenable extensions by additional CPUs, GPU, and the like. The peripheraldevices can be attached either directly to the core's system bus (1648),or through a peripheral bus (1649). Architectures for a peripheral businclude PCI, USB, and the like.

CPUs (1641), GPUs (1642), FPGAs (1643), and accelerators (1644) canexecute certain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM(1645) or RAM (1646). Transitional data can be also be stored in RAM(1646), whereas permanent data can be stored for example, in theinternal mass storage (1647). Fast storage and retrieve to any of thememory devices can be enabled through the use of cache memory, that canbe closely associated with one or more CPU (1641), GPU (1642), massstorage (1647), ROM (1645), RAM (1646), and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture (1600), and specifically the core (1640) can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core (1640) that are of non-transitorynature, such as core-internal mass storage (1647) or ROM (1645). Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core (1640). Acomputer-readable medium can include one or more memory devices orchips, according to particular needs. The software can cause the core(1640) and specifically the processors therein (including CPU, GPU,FPGA, and the like) to execute particular processes or particular partsof particular processes described herein, including defining datastructures stored in RAM (1646) and modifying such data structuresaccording to the processes defined by the software. In addition or as analternative, the computer system can provide functionality as a resultof logic hardwired or otherwise embodied in a circuit (for example:accelerator (1644)), which can operate in place of or together withsoftware to execute particular processes or particular parts ofparticular processes described herein. Reference to software canencompass logic, and vice versa, where appropriate. Reference to acomputer-readable media can encompass a circuit (such as an integratedcircuit (IC)) storing software for execution, a circuit embodying logicfor execution, or both, where appropriate. The present disclosureencompasses any suitable combination of hardware and software.

Appendix A: Acronyms

-   JEM: joint exploration model-   VVC: versatile video coding-   BMS: benchmark set-   MV: Motion Vector-   HEVC: High Efficiency Video Coding-   SEI: Supplementary Enhancement Information-   VUI: Video Usability Information-   GOPs: Groups of Pictures-   TUs: Transform Units,-   PUs: Prediction Units-   CTUs: Coding Tree Units-   CTBs: Coding Tree Blocks-   PBs: Prediction Blocks-   HRD: Hypothetical Reference Decoder-   SNR: Signal Noise Ratio-   CPUs: Central Processing Units-   GPUs: Graphics Processing Units-   CRT: Cathode Ray Tube-   LCD: Liquid-Crystal Display-   OLED: Organic Light-Emitting Diode-   CD: Compact Disc-   DVD: Digital Video Disc-   ROM: Read-Only Memory-   RAM: Random Access Memory-   ASIC: Application-Specific Integrated Circuit-   PLD: Programmable Logic Device-   LAN: Local Area Network-   GSM: Global System for Mobile communications-   LTE: Long-Term Evolution-   CANBus: Controller Area Network Bus-   USB: Universal Serial Bus-   PCI: Peripheral Component Interconnect-   FPGA: Field Programmable Gate Areas-   SSD: solid-state drive-   IC: Integrated Circuit-   CU: Coding Unit

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof

What is claimed is:
 1. A method of video decoding performed in a video decoder, the method comprising: receiving coded information of neighboring blocks of a current block from a coded video bitstream, the coded information comprising intra prediction information of the neighboring blocks; determining intra prediction information of the current block based on the coded information of the neighboring blocks; determining an intra prediction direction mode based on the intra prediction information of the current block; and reconstructing at least one sample of the current block according to the intra prediction direction mode of the current block.
 2. The method of claim 1, wherein the determining the intra prediction information of the current block comprises: determining a context model from a set of context models based on the coded information; and determining the intra prediction information of the current block based on the coded information of the neighboring blocks of the current block according to the determined context model.
 3. The method of claim 2, wherein the coded information comprises at least one of an MPM flag, a reference line index, an intra sub-partition (IPS) flag, an intra prediction mode, or an MPM index.
 4. The method of claim 3, wherein the intra prediction information of the current block comprises at least one of a most probable mode (MPM) flag, a size of an MPM list, or an MPM index.
 5. The method of claim 2, wherein the determining the context model from the plurality of context models based on the coded information comprises: determining the context model based on at least one of a number of non-angular modes of the neighboring blocks, a number of angular modes of the neighboring blocks, MPM flags of the neighboring blocks, MPM indices of the neighboring blocks, or ISP flags of the neighboring blocks.
 6. The method of claim 4, wherein the size of the MPM list of the current block is equal to a first integer when intra prediction modes of the neighboring blocks are non-angular modes, and the size of the MPM list of the current block is equal to a second integer when one of the intra prediction modes of the neighboring blocks is an angular mode, the first integer being smaller than the second integer.
 7. The method of claim 4, wherein the size of the MPM list of the current block is equal to a first integer when intra prediction modes of the neighboring blocks are non-angular modes, the size of the MPM list of the current block is equal to a second integer when one of the intra prediction modes of the neighboring blocks is a non-angular mode, and the size of the MPM list of the current block is a third integer when the intra prediction modes of the neighboring blocks are angular modes, the first integer being smaller than the second integer, the second integer being smaller than the third integer.
 8. A method of video decoding performed in a video decoder, the method comprising: receiving coded information of a current block and neighboring blocks of the current block from a coded video bitstream, the coded information comprising intra prediction information of the current block and the neighboring blocks; decoding first information associated with the current block in the coded information, wherein the first information indicates whether an intra prediction mode for luma samples of the current block belongs to selected intra prediction modes; decoding second information associated with the current block in the coded information responsive to the first information indicating that the intra prediction mode for luma samples of the current block belongs to the selected intra prediction modes, the second information indicating whether a most probable mode (MPM) for luma samples of the current block is an angular mode or a non-angular mode; decoding third information associated with the current block in the coded information, wherein the third information indicates an MPM index for the luma samples of the current block, responsive to the second information indicating the MPM for the luma samples of the current block is the angular mode; and decoding fourth information associated with the current block in the coded information, wherein the fourth information indicates whether the MPM of the current block is a Planar mode or a DC mode, responsive to the second information associated with the current block indicating the MPM for the luma samples of the current block is the non-angular mode.
 9. The method of claim 8, wherein a context model used for entropy coding the second information associated with the current block is determined based on the first information associated with the neighboring blocks or the second information associated with the neighboring blocks.
 10. The method of claim 8, wherein the third information associated with the current block is coded using a fixed length coding.
 11. An apparatus for video decoding, comprising: processing circuitry configured to: receive coded information of neighboring blocks of a current block from a coded video bitstream, the coded information comprising intra prediction information of the neighboring blocks; determine intra prediction information of the current block based on the coded information of the neighboring blocks; determine an intra prediction direction mode based on the intra prediction information of the current block; and reconstruct at least one sample of the current block according to the intra prediction direction mode of the current block.
 12. The apparatus of claim 11, wherein the processing circuitry is configured to: determine a context model from a set of context models based on the coded information; and determine the intra prediction information of the current block based on the coded information of the neighboring blocks of the current block according to the determined context model.
 13. The apparatus of claim 12, wherein the coded information comprises at least one of an MPM flag, a reference line index, an intra sub-partition (IPS) flag, an intra prediction mode, or an MPM index.
 14. The apparatus of claim 13, wherein the intra prediction information of the current block comprises at least one of a most probable mode (MPM) flag, a size of an MPM list, or an MPM index.
 15. The apparatus of claim 12, wherein the processing circuitry is configured to: determine the context model based on at least one of a number of non-angular modes of the neighboring blocks, a number of angular modes of the neighboring blocks, MPM flags of the neighboring blocks, MPM indices of the neighboring blocks, or ISP flags of the neighboring blocks.
 16. The apparatus of claim 14, wherein the size of the MPM list of the current block is equal to a first integer when intra prediction modes of the neighboring blocks are non-angular modes, and the size of the MPM list of the current block is equal to a second integer when one of the intra prediction modes of the neighboring blocks is an angular mode, the first integer being smaller than the second integer.
 17. The apparatus of claim 14, wherein the size of the MPM list of the current block is equal to a first integer when intra prediction modes of the neighboring blocks are non-angular modes, the size of the MPM list of the current block is equal to a second integer when one of the intra prediction modes of the neighboring blocks is a non-angular mode, and the size of the MPM list of the current block is a third integer when the intra prediction modes of the neighboring blocks are angular modes, the first integer being smaller than the second integer, the second integer being smaller than the third integer.
 18. An apparatus for video decoding, comprising: processing circuitry configured to: receive coded information of a current block and neighboring blocks of the current block from a coded video bitstream, the coded information comprising intra prediction information of the current block and the neighboring blocks; decode first information associated with the current block in the coded information, wherein the first information indicates whether an intra prediction mode for luma samples of the current block belongs to selected intra prediction modes; decode second information associated with the current block in the coded information responsive to the first information indicating that the intra prediction mode for luma samples of the current block belongs to the selected intra prediction modes, the second information indicating whether a most probable mode (MPM) for luma samples of the current block is an angular mode or a non-angular mode; decode third information associated with the current block in the coded information, wherein the third information indicates an MPM index for the luma samples of the current block, responsive to the second information indicating the MPM for the luma samples of the current block is the angular mode; and decode fourth information associated with the current block in the coded information, wherein the fourth information indicates whether the MPM of the current block is a Planar mode or a DC mode, responsive to the second information associated with the current block indicating the MPM for the luma samples of the current block is the non-angular mode.
 19. The apparatus of claim 18, wherein a context model used for entropy coding the second information associated with the current block is determined based on the first information associated with the neighboring blocks or the second information associated with the neighboring blocks.
 20. The apparatus of claim 18, wherein the third information associated with the current block is coded using a fixed length coding. 